A vehicle, such as an automobile, is generally equipped with an airbag device for absorbing impact applied to an occupant in case of emergency, such as a collision or an abrupt deceleration, by deploying an airbag in a vehicle. Various types of airbag devices have been developed and used. Examples of such an airbag device include a driver airbag device disposed in a steering wheel, a passenger airbag device disposed behind an instrument panel, a side airbag device disposed in a vehicle side portion or a seat, a curtain airbag device disposed in an upper portion of a door, a knee airbag device for the knees of an occupant, and a pedestrian airbag device disposed below the hood.
Such an airbag device generally includes an airbag that is folded in a normal state and deployed in case of emergency, an inflator that supplies gas to the airbag, and a retainer that secures the airbag and the inflator. The airbag may be provided with, for example, a strap which regulates the shape into which the airbag is deployed or controls an open/closed state of a vent hole (see, for example, PTL 1 to PTL 4).
An airbag device described in PTL 1 includes a strap-retaining device, which includes a pin element and a squib, and a patch element (strap) that is connected to the outer surface of an airbag at one end thereof and engageable with the pin element at the other end thereof. An open/closed state of a vent hole is controlled by controlling a retained/released state of the patch element (see, for example, FIGS. 4 to 7 of PTL 1). When the patch element is released from the pin element, the patch element is ejected to the outside of the airbag through the vent hole by a tension applied thereto, so that the vent hole is opened (see, for example, FIG. 7 of PTL 1).
An airbag device described in PTL 2 includes a connection selection mechanism (strap-retaining device), which includes an actuator, and a connecting element (strap) that is connected to the outer surface of an airbag at one end thereof and engaged with a retaining portion, which is disposed adjacent to the connection selection mechanism, at the other end thereof. An open/closed state of a vent hole is controlled by controlling a retained/released state of the connecting element (see, for example, FIGS. 1 to 13 of PTL 2). When the connecting element is released from the retaining portion by an operation of the connection selection mechanism, the connecting element is pulled out of the airbag by a tension applied thereto, so that the vent hole is opened (see, for example, FIG. 13 of PTL 2).
An airbag device described in PTL 3 includes an actuator (strap-retaining device), which includes a cutter and a gas generating device, and a tether (strap) that is connected to a duct portion that projects out of an airbag at one end thereof and engageable with the actuator at the other end thereof. An open/closed state of a vent hole, which is formed in the duct portion, is controlled by controlling a retained/released state of the tether (see, for example, FIG. 4 of PTL 3). When the tether is cut off and released by an operation of the actuator, the tether is pulled out of the airbag by a tension applied thereto, and the duct portion is reversed so that the vent hole is opened.
An airbag device described in PTL 4 includes a strap-retaining device, which includes a cap and a releasing device, and a strap that is connected to a projecting portion, which is formed so as to project out of an airbag, at one end thereof and capable of being engaged with the strap-retaining device by the cap at the other end thereof. An open/closed state of a vent hole, which is formed in the projecting portion, is controlled by controlling a retained/released state of the strap (see, for example, FIG. 5 of PTL 4). When the cap is blown away by an operation of the releasing device, the tether is pulled out of the airbag by a tension applied thereto, and the projecting portion stands on the airbag so that the vent hole is opened. Furthermore, FIG. 19 of PTL 4 illustrates that the volume of the airbag (shape thereof in a deployed state) can also be controlled by a similar operation.